When the former chief of The Police went solo in 1985 and started releasing socially conscious jazz-rock albums, the critics rallied and launched a massive smear campaign. ''Who does this millionaire, pretty-boy rock star think he is, making grand statements about war and peace and South American politics?'' they asked. ''And who told an Englishman he could play jazz?''

When Sting didn't go away as they'd hoped, the critics turned ugly. One well-placed New York City scribe recently printed a desire to ''bash (Sting's) head against a wall.''

If by now you hadn't dismissed all this foaming at the mouth as proof of how juvenile critics can be, Sting buried the subject himself Tuesday night at the sold-out Riverside Theater.

A masterful bandleader and performer, Sting pitched an eloquent argument that it is the brain, not just the beat, that makes rock music tick.While Sting often makes cool, studied music on his solo records, he thrives on the element of surprise onstage.

The message Sting and his eight-piece band offered time and again in the two and a half hour concert was that nothing should be taken for granted: Reggae-zed Police hits such as 'Roxanne' turned into sparse, mournful ballads. The flamenco sounds of Sting's 'Fragile' disappeared into a roaring jazz-fusion version of Jimi Hendrix's 'Little Wing', then segued into a heavy-metal attack on the Beatles' 'From Me To You'.

Even in numbers that seemed fairly straightforward, Sting found a way to use them as springboards for new musical ideas. The snappy jazz song 'Englishman in New York' became a launching pad for swaggering funk rock, and more than a few concise pop numbers spawned long, jazz-rock jam sessions.

With world class players such as percussionist Mino Cinelu and saxophonist Branford Marsalis in Sting's band, the jazz-fusion workouts never became tiresome.

In reality, all those breathtaking zigzags had been mapped out before the tour even started. But even if music that seemed spontaneous was actually a case of Sting using trickery, the results were nonetheless moving. In his show-closing solo rendition of 'Message in a Bottle', Sting softened his vocals slightly to give the audience a chance to sing the chorus.

When they did, he stopped in his tracks and began a graceful harmony with them - seemingly off the top of his head. Sleight of hand or not, it worked beautifully.

Sting wasn't flawless Tuesday. His attempt at a grandiose ending for 'Don't Stand So Close to Me' was painfully overblown. He and the band drowned out some of Marsalis' best saxophone solos. And his chest-baring act during the encore was a fairly stupid way to cap an evening of thought-provoking music. But Sting gave fans a glimpse of something many of them didn't know existed - a sense of humour.

From his existential lyrics to his grim-looking publicity photos Sting usually depicts himself as rock's tortured soul. As he put it in song, ''It is my destiny to be the King of Pain.''

But Tuesday found Sting smiling often, cracking jokes, and indulging in comical dance work. Many of his songs carry heavy themes, but by lightening up in concert Sting deflated critics who sneer at him for being a glum, pretentious rock intellect.